Re: [PATCH 2/5] mm/huge_memory: dequeue the deferred split after the split freeze

[Johannes Weiner]

On Wed, Aug 26, 2026 at 05:20:58PM +0100, Kiryl Shutsemau wrote:
> From: "Kiryl Shutsemau (Meta)" <kas@xxxxxxxxxx>
> 
> __folio_freeze_and_split_unmapped() takes the deferred split list_lru lock
> across the freeze. It is only there to stop deferred_split_scan() from
> touching the folio under split.
> 
> With deferred_split_isolate() fixed, the workaround can be dropped.
> 
> Unqueue the folio after folio_ref_freeze(), the way
> __folio_migrate_mapping() does: folio_unqueue_deferred_split() needs a
> zero refcount and a memcg still set, and both hold there.
> 
> If the split is called from deferred_split_scan(), the unqueue is a
> no-op -- the folio is already removed from the list. But
> PG_partially_mapped is still set, so it has to be cleared here or
> MTHP_STAT_NR_ANON_PARTIALLY_MAPPED never comes back down.
> 
> Assisted-by: Claude-Code:claude-opus-5
> Signed-off-by: Kiryl Shutsemau (Meta) <kas@xxxxxxxxxx>

Infinitely better!

Reviewed-by: Johannes Weiner <hannes@xxxxxxxxxxx>